Speed should be at the cost of efficiency. Air should be inefficient, perhaps a small amount more than next build. Bot fabbers should, like air fabbers, be fast, lightly armored, inefficient fabbers, about half as inefficient as air. Fab subs should be in the middle, as a tradeoff for their stealth and the fact that they're hard to hit. Vehicle fabs should be more efficient than bots, but slower and maybe 50 metal more expensive. Fab ships should be the slowest and most efficient. Orbital... Logically they should be the most efficient, given that they should have onboard solar panels, but I don't know if that would be very balanced. Thoughts on them?
Not sure about the bots vs vehicles thing. by efficiency do you mean build speed or energy consumption? i think it would be interesting if bots and vehicles had different build rates and/or energy consumption, but cost the same.
